Circuit breaker



March ll, 1.930. A. coRBETT CIRCUIT BREAKER Filed Dec. 51, l1927 I I f i aa/ l aafla INVENToR /l/ed Core# ATTRNEY Patented` Mar. 1l, 1930 PATENT oFFlcE l ALFRED COBBETT, OF IRWIN, PENNSYLVANIA, ASSIGNOR '10 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA CIRCUIT BREAKER Application filed' December 31, 1927. Serial No. 243,879.4

.is reduced to a minimum and is rapidly cooled and extinguished before the contacts are burned by the arc. v

A further object of my invention is to provide circuit breaker contacts and arc extinguishing mechanism therefor having the above-noted characteristics wherein a shunt path is provided for separating the are from a -contact when the contacts have separated a predetermined distance. i

These and other objects that ,will be made apparent throughout the further description of my invention, are attained by means of the apparatus hereinafter described and illustrated in the accompanying drawings Where- Figure 1 is a longitudinal sectional view through a circuit breaker embodying features of my invention, the circuit breaker operating mechanism being shown in elevation; Fig. 2 is a plan view of the contacts and arc 'extinguishing mechanism Fig. 3 is a transverse section through a portion of the circuit breaker apparatus taken on the line III-III of Fig. 2; and

Fig. 4 is a longitudinal section through a portion of the circuit breaker apparatus taken on the line IV--IV of Fig; 2?- i Referring to the drawings,my improved circ-uit breaker contacts and arc extinguishvring mechanism are illustrated as applied to a circuit breaker of the type disclosed in.

the copending application of Mr. Fred G. Von Hoorn, Serial No. 212,289, filed August 11, 1927, and assignedto the Westinghouse Electric & Manufacturing Company. Circuit breakers of this type are current responsive, the circuit breaker being released to open position by means of a bimetal thermal element connected in the circuit breaker circuit. Briefly, the circuit breaker comprises an insulating base 5 upon which the contact and arc extinguishing mechanism 6 is mounted. A circuit breaker is also mounted on the insulating base and comprises a supporting frame 7 upon which a contact arm 8 is pivoted. The Contact arm is actuated by a pair of toggle links 9` and 10 that are pivotally `ioined by a knee pivot 11. The link 9 is pivoted to the contact arm 8 and the link 10 is pivotally mounted in a V-notch l2 provided on a toggle carrier 13 that is pivoted atll to the frame 7 and which is releasably retained in the vposition indicated in dotted lines in Fig. 1 by means of a bi-v metal thermal element 20.l

An operating handle 15, pivoted for rotation about the shaft 16 is connected to the knee pivot 11 of the toggle by means of an over-center spring 17. As indicated in Fig. 1, the parts are shown in the position occupied when the circuit breaker is` in full open and current released position. When the carrier 13 is in the position indicated in dotted lines, the contact arm is moved to open and close position by the operating handle 15 which causes the contact arm to move with a snap actionA after the outer end of the spring 17 has moved over center.

Since the circuit breaker construction constitutes no part of my invention, it is believed unnecessary to go ihtoi further details of the operation of the circuit breaker except to state that it is of the type that opens and closes with a snap action and is responsive to overload and short circuit current condi- 4tions'to open the circuit breaker.

The contact an 8 is provided with a ing contact member-18that is of U-shape as indicated in Fig. 3. The bridging contact is preferably made of copper and is provided with nickel contact tips 19 that are adapted to engage, when the contact arm 8 is in closed position, stationary contact plates 21 that are separate preferably made of silver block. The contact plates 21 are connected to terminals 22 and 23 by means of conductors 24.

The contact lates 21 are mounted in an insulatin housing block 25, the plates being b an lnsulating barrier wall 26 which divi es the block into two compartments 27 and 28 each containing a contact member 21, and the arc extinguishing barriers to be hereinafter described. Superimposed above each contact member 21, and in each of the compartments, are located a plurality of sheet iron barrier plates 29 that are spaced apart by insulating plates 31. The lates 31 are separated to provide an air channel 32 therebetween as indicated in Figs.

,2 and 3, through which arc gases may escape.

The plates are each provided with aligned slots 33 for receiving the Contact legs of the bridging contact 18, just sutlicient clearance being rovided to prevent engagement of the legs of3 the bridging contact with the barrier plates. The innermost late is spacedfrom the contact plate 21 andp barrier plate 34, of sutiicient length to cover both groups of plates 29 is mounted in superimposed relation to thev said groups and insulated from plates 29 as indicated in Figs. 2 and 3. The outermost plate is provided 3g with slots that align with the slots 33 and ,s 606,565 filed by which permit of movement yof the bridging contact into engagement with the silver contacIts 21. d Se N n the copen a' plication rial o. 01.115. Jrdnnings December 13, 1922, and assigned to the Westinghouse Electric & Manufacturing Company, circuit breaker apparatus is disclosed having slotted barriers somewhat similar to the barriers 29 for extinguishin the arc incident to the separation of a kni e blade from ielding contact jaws..- The knife blades lllustrated in that application are connected in a multiphase circuit and the contacts thereof are not connected in series, and consequently, interrupt the circuit of each phase at one point only. In the present case, a bridging switch is used for connecting the contacts 21 in series, thus insuring a double break which reduces the arc voltage by reason thereof. In addition, the present barrier construction is provided with a top barrier plate that covers the groups of barrier plates 29, this plate serving as a shunt for the circuit maintained by the arc incident to the separation of the contacts and thus causin separation of the arc from the bridging contact 18, the instant an arc engages the outermost plate 34.

It has beenl found that, when an arc is drawn in the slots of a series of iron plates insulated from one another, that the mag-A net-ic field of the arc causes the arc to move from the slots into the stack of plates where the permeability is eater than that of the slots. Movement o? the are into the stack an outer sheet-iron breaks it up into a series of arcs, one between each pair of plates.

When the circuit breaker is opened under normal load conditions, the current nterrupted is relatively small and any arc drawn between the contacts-upon separation is instantly cooled by the barriers and extinguished.

In operation, under severe overload or short-circuit conditions the arc drawn between the nickel and silver contacts first comes in contact with the edges of the slots of the innermost barrier plate 29. As the bridging contact moves outwardly past the first plate, the arc is moved into the s ace between the first and second plates and i the arc still endures, it finally is drawn between the second and third or outermost plate. W'hen this occurs, the current passes through the plate 34 which immediately disconnects the bridging contact 18 from the circuit.

It ,is well known that a'considerable voltage drop occurs at the electrodes between which an arc is established. In the present instance, the current must pass through six separate arcs, each having an equal and substantial resistance thus reducing the` voltage below a point at which an arc may be sustained in the air gap provided between the plates. It has been found that at least 30 volts are required to maintain an arc between a contact and one of the lates, and, therefore, if sutlicient number o lates are introduced to reduce the voltage 1n the arc circuit below the voltage specified, an are cannot be maintained. Consequently, the circuit is interrupted when the bridging conact has drawn the arc past agsutiicient number of barrier plates to reduce the voltage below4 the specified amount. It is thus apparent that the arc will be extinguished, 1n case of alternating current in less than a full c cle and that in the case of direct current, t e arc will be extinguished immediately after the voltage is reduced below a.l predetermined amount.

When the arc engages the edges of the slots in the iron plates, 1t expands outwardly between them and is immediately cooled thus assisting iri extinguishing the arc.

By reason of the arc extin ishing barrier construction above descri ed, lar e current values may. be interruptedwit out` injury to the contacts which may be used lrepeatedly for interrupting the cirrelatively cuit under load and short circuit conditions,

tions and omissions may be made in the apparatus illustrated Without departing from the spirit and scope of my invention as set forth in the appended claims.

I claim as my invention:

1. A circuit breaker comprising a pair of spaced contact members,'a pair yof connected .i

spaced contact blades forI engaging thesaid contact members, a separate metal are' quenching barrier for each blade disposed across the path of movement of the blade c and provided with an opening through which the blade moves, the said barriers being -spaced and insulated from the contact members, and a metal arc quenching barrier superimposed in spaced relation to the first bar riers and provided with openings through which the blades move.

2. A circuit breaker comprising a pair of 4:paced contact members, a pair of contact blades for engaging the contact members, a plurality of metal arc quenching barrier plates superimposed in spaced relation upon the contact members, the said plates being insulated from the Contact members and from one another, the innermost plates being separate and provided with openings through which contact blades may pass in moving into and out of engagement with the contact members, and the outermost plates being conductively connected.

3. A circuit breaker comprising an insulating block having a recess divided into two compartments by an insulating parti- Arion, a contact member mounted in each compartment, connected contact blades for engaging the contact members, a group of spaced metal plates in each compartment superimposed upon one another and upon the contact member in each compartment, and a metal plate superimposed upon the plates of both groups, the said plates having aligned openings through which contact blades pass in moving into and out of engagement with the contact members.

4. In a circuit breaker the combination with a pair of contact members and a bridging contact therefor having spaced parallel contact blades, of separate superimposed spaced metal plates having openings therein through which the contact blades move and substantially surrounding the blades and a single plate superimposed upon the said plates in spaced relation thereto and insulated therefrom. and provided with openings ber, 1927.

registering with the openings in the said spaced plates.

In testimony whereof, I have hereunto subscribed my name this 29th day. of Decem- ALFRED' RBTT. 

